The invention relates to a fluidized bed reactor for the cultivation of immobilised biocatalysts suspended in effluent with fittings for gassing and a retainer system for the immobilised biocatalysts. Also, the invention relates to a process for the operation of the fluidized bed reactor.
Increasingly, micro-organisms or enzymes are bound to special carriers in the cleaning of effluent and in enzymatic reactions, in order to achieve a heightened activity of the biocatalysts. Fixed bed and fluidized bed reactors are used as reactors. In fixed beds, the biocatalysts are often only partly utilized because of uneven packing or because of an uneven growth of the organisms. The process can also be disadvantageously influenced (e.g. through changes in pH) by concentration gradients in the fixed bed. Accordingly it is better, in many processes, to use a fluidized bed reactor in which a sufficient mixing of the fluid phase occurs, so that the carriers are in a suspended state or can be temporarily fluidized.
The energy for fluidizing can be either introduced via the fluid phase (by pump recirculation) or by gassing the fluid-solid mixture. The gas-operated fluidized bed is an especially useful reactor type for aerobic fermentation processes. A reduction of the energy introduced for fluidizing the biocatalysts is made possible by building in guides, such as e.g. baffle plates or guide tubes. In large installations, the fluctuating movements that often arise in gas-operative fluidized beds give rise to serious oscillations in the fittings which has often lead to the destruction of the guides or their anchorages.
In continuous processes, there is a further problem in the retention of the often expensive biocatalysts in the reactor. The customary method of retention by filtration is in many cases not practicable, as the filters block up and/or only low filtrate flow rates are achieved, which in turn necessitate large filter surfaces, thus causing high costs.